You might have an API method of different structure type that you want to expose under the same name.

Example
You have web service method X and web service method Y, they use structure AddressX and AddressY, (two different structures) for two different services, but when you expose the structure under the same json structure name "Address", you also want the structure model documented the same name "Address".

Note: You might even have an entity titled "Address" therefore you can not name your structure "Address", but you do want to pubically EXPOSE your rest web service json structure/model under the same name - "Address".